Cement admixtures comprising polycarboxylic acid polymers have been widely used for cement compositions such as cement paste, mortar, and concrete. They are now essential in constructing civil engineering and building structures and the like from cement compositions. Such cement admixtures are used as water reducing agents; they increase the fluidity of cement compositions to thereby reduce the water requirement of the cement compositions and therefore are effective in improving the strength, durability, and the like, of hardening products. Such water reducing agents are superior in water-reducing performance to naphthalene and other conventional water reducing agents and thus have already led to good results in many cases as air-entraining and high-range water-reducing admixture.
Meanwhile, cement admixtures are required to be able not only to show water-reducing performance in such cement compositions but also to improve cement compositions in viscosity to thereby facilitate the works at the sites of handling them. Thus, while cement additives used as water reducing agents show their water-reducing performance by reducing the viscosity of cement compositions, they are required at the sites of civil engineering and building structure construction not only to be able to show their performance to reduce the viscosity of cement compositions but also to provide a viscosity in such the level that the works will be facilitated at the sites of handling them. If a cement admixture can exhibit such performance characteristics, it will improve the working efficiency in civil engineering and building structure construction.
Japanese Kokai Publication 2000-191356 discloses that a cement dispersant whose main component is a water-soluble amphoteric copolymer obtained by copolymerization of a specific polyamine-derived monomer as compound A, a specific unsaturated carboxylic acid monomer as compound B and a specific polyalkylene glycol-derived monomer as compound C in the proportion of compound A: compound B: compound C=10 to 40% by mass : 10 to 40% by mass: 50 to 80% by mass can be used as a dispersant for ultrahigh strength concrete and that it is excellent in field workability.
However, water-soluble amphoteric copolymers prepared in all Examples in this publication by copolymerizing compound A, compound B and compound C, when used in preparing high strength concrete, provide them with high viscosity, making the shovel work difficult; thus, they have a workability problem. Therefore, there was room for contrivance in order to be able to applied to various cement compositions and the like suitably, in addition, to provide such a level of viscosity as facilitating the works on the sites of handling them.